KR20120104319A - Metrology for extreme ultraviolet light source - Google Patents

Abstract

The extreme ultraviolet light system includes a drive laser system for producing an amplified light beam; A target material delivery system configured to produce a target material at a target location; A beam delivery system configured to receive an amplified light beam emitted from the drive laser system and redirect the amplified light beam toward a target position; And a metrology system. The beam delivery system includes a converging lens constructed and arranged to focus the amplified light beam at the target location. The metrology system includes a light collection system configured to collect a portion of the amplified light beam reflected from the converging lens and a portion of the guide laser beam reflected from the converging lens. The light collection system includes a dichroic optical device configured to optically separate the portions.

Description

Metrology for extreme ultraviolet light sources {METROLOGY FOR EXTREME ULTRAVIOLET LIGHT SOURCE}

The disclosed invention relates to a metrology system for an extreme ultraviolet light source.

Extreme ultraviolet (“EUV”) light, such as electromagnetic radiation (sometimes called soft X-rays) having a wavelength of about 50 nm or less and comprising light of approximately 13 nm, is very small on a substrate such as a silicon wafer. It can be used in photolithography processes to create features.

The method of producing EUV light includes, but is not limited to, converting the material into a plasma state comprising an element having an emission line in the EUV range, such as xenon, lithium, or tin. In one such method, often referred to as laser generated plasma (“LPP”), the required plasma is an amplified light beam that can be called a driving laser, for example irradiating a target material in the form of droplets, streams or clusters of material. Can be made. During this process, the plasma is typically made in a sealed container such as a vacuum chamber and monitored using various types of metrology equipment.

C0 ₂ amplifiers and lasers that output an amplified light beam with a wavelength of approximately 10600 nm may exhibit certain advantages as drive lasers irradiating target material in an LPP process. This is especially true for certain target materials, for example for materials containing tin. For example, one advantage is that it can yield a relatively high conversion efficiency between drive laser input power and output EUV power. Another advantage of C0 ₂ drive amplifiers and lasers is that relatively long wavelengths of light (e.g., compared to deep UV at 198 nm) may be reflected from relatively rough surfaces, such as reflective optics covered with tin debris. Can be. This property of 10600 nm radiation enables the reflection mirror to be used near the plasma to adjust, for example, steering, focusing, and / or adjusting the amplified light beam.

In some general forms, an extreme ultraviolet light system includes a drive laser system that produces an amplified light beam; A target material conveying system configured to produce a target material at a target location in a vacuum space formed in the chamber; A beam delivery system comprising a set of optical components; Measurement system; And a controller. The beam delivery system is configured to receive the amplified light beam emitted from the drive laser system and to direct the amplified light beam toward a target position. The vacuum chamber includes an extreme ultraviolet light collector configured to collect extreme ultraviolet light emitted from the target material when the amplified light beam strikes the target material across the target location. The metrology system includes a light collection system and a light sensor. The light collection system is configured to collect a diagnostic portion of the amplified light beam that does not reach at least the target position and a diagnostic portion of the guide laser beam that does not reach at least the target position. The light collection system comprises a dichroic optical device configured to separate the diagnostic portions by substantially transmitting all of the diagnostic portions and substantially reflecting all of the other diagnostic portions, wherein the at least two diagnostic portions are distinguished. Has a wavelength. The optical sensor captures at least two diagnostic portions separated by a dichroic optical device. The controller is coupled to the light sensor and to the at least one component for adjusting the position of the at least one component in the beam delivery system based on the output of the light sensor.

Implementations may include one or more of the following features. For example, the beam delivery system includes a beam expanding system that enlarges the size of the amplified light beam; And a focusing element configured and arranged to focus the amplified light beam to a target position.

The focusing element may comprise a converging lens. The converging lens can be an aspheric lens. The converging lens can be made of zinc selenide. The converging lens may comprise an antireflective coating and may transmit at least 95% of light at the wavelength of the amplified light beam. The converging lens may form a pressure resistant window of the vacuum chamber for isolating the vacuum inside the vacuum chamber from the external environment of the vacuum chamber. The converging lens can have a numerical aperture of at least 0.25.

The beam delivery system may include an actuation system mechanically coupled to the converging lens, which receives the control signal from the controller and adjusts the convergence lens to focus the amplified light beam based on the control signal. It is configured to move.

The light collection system can be configured to collect the amplified light beams reflected by one side of the converging lens.

The beam delivery system may include a pre-lens mirror that redirects the amplified light beam from the beam expanding system back toward the converging lens. The beam delivery system may include an actuation system mechanically connected to the mirror in front of the lens, the actuation system receiving a control signal from the controller and adjusting the focus of the amplified light beam based on the control signal. Configured to move the front mirror.

The controller is coupled to the at least one component to change the position of the at least one component to increase the overlap between the target material at the target position and the amplified light beam, thereby increasing the generation of extreme ultraviolet light in the chamber. It can be configured to provide an output signal to the actuation system.

The metrology system may be a closed-loop feedback system.

The system may include a guide laser to produce a guide laser beam. The amplified light beam may be a first distinct wavelength and the guide laser beam may be a second distinct wavelength. The dichroic optical device may be configured to separate the amplified light beam diagnostic portion from the guide laser beam diagnostic portion by substantially reflecting the entire amplified light beam diagnostic portion and substantially transmitting the entire guide laser beam diagnostic portion. .

In another general form, extreme ultraviolet light produces a target material at a target location inside a vacuum formed by the chamber; Supply pump energy to a gain medium of at least one optical amplifier in the drive laser system to produce an amplified light beam; Alter one or more characteristics of the amplified light beam and direct the amplified light beam through a set of optical components to a target location; Directing the guide laser beam to a target position; Collect at least a portion of the amplified beam that does not reach the target position and at least a portion of the guide laser beam that does not reach the target position; One of the collected portions is transmitted through the dichroic optical member, and the collected amplified light beam portion and the collected guide laser beam portion are transferred to the dichroic optical device such that the other portion of the collected portions is reflected from the dichroic optical member. Is generated by separating the collected amplified light beam portion from the collected guide laser beam portion.

Implementations may include one or more of the following features. For example, the separated portion can be sent to an optical sensor that outputs image data of the separated portion.

Image data of each separated portion can be sent to an analysis module, which determines the beam size of the image data for each separated portion and determines the center of the image data for each separated portion. Configured to perform one or more of the things.

The position of one or more components of the optical component set may be adjusted based on one or more of the determined beam size and the determined center.

The amplified light beam is one set by reflecting the amplified light beam from the mirror and directing the reflected and amplified light beam to a target position through a focusing element that captures the amplified light beam and focuses the amplified light beam. It can be oriented through the optical component of. These parts can be collected by collecting the part reflected back from the converging lens through the opening in the mirror.

In another general form, an extreme ultraviolet light system includes a driving laser system that produces an amplified light beam, a target material conveying system, a beam delivery system, and a metrology system. The target material delivery system is configured to produce the target material at a target location in the vacuum formed within the chamber. The vacuum chamber houses an extreme ultraviolet light collector configured to collect the extreme ultraviolet light emitted from the target material when the amplified light beam strikes the target material across the target location. The beam delivery system is configured to receive the amplified light beam emitted from the drive laser system and to direct the amplified light beam toward a target position. The beam delivery system includes a set of optical components including a converging lens constructed and arranged to focus the amplified light beam at a target location. The metrology system includes a light collection system configured to collect a portion of the amplified light beam reflected from the converging lens and a portion of the guide laser beam reflected from the converging lens. The light collection system includes a dichroic optical device configured to separate the portions by transmitting the first portion and reflecting the second portion.

Implementations may include one or more of the following features. For example, the system also includes an optical sensor that captures portions separated by a dichroic optical device, and within the beam delivery system to reposition the at least one component based on and at the output from the optical sensor. It may include a controller connected to at least one component. The controller is actuated to at least one component of the beam delivery system to change the position of the at least one component to increase the generation of extreme ultraviolet light in the chamber by increasing the overlap between the target material at the target position and the amplified light beam. It can be configured to provide an output signal to the system.

The system may include an actuation system mechanically coupled to the converging lens, which receives the control signal from the controller and moves the converging lens to adjust the focus of the amplified light beam based on the control signal. It can be configured to.

The beam delivery system may include a lens front mirror that redirects the amplified light beam from the beam expanding system back towards the converging lens. The amplified light beam portion and the guide laser beam portion reflected from the converging lens can be oriented through an opening in the mirror in front of the lens before reaching the dichroic optical device. The beam delivery system may include an actuation system mechanically coupled to the front lens of the lens. The actuation system may be configured to receive a control signal from the controller and to move the mirror in front of the lens to adjust the focus of the amplified light beam based on the control signal.

The converging lens can form a pressure resistant window of the vacuum chamber for isolating the vacuum space from the outer space.

The amplified light beam may be of a first distinct wavelength. The system may also include a guide laser that produces a guide laser beam that is a second distinct wavelength.

The beam delivery system may include a beam expanding system that magnifies the size of the amplified light beam. The converging lens can be configured and arranged to receive the amplified amplified light beam from the beam expanding system.

The converging lens can have a numerical aperture of at least 0.25.

The system may also include a guide laser to produce a guide laser beam. In this case, the amplified light beam may be the first distinct wavelength, the guide laser beam is the second distinct wavelength, and the dichroic optical device reflects substantially all of the amplified light beam diagnostic portion and the guide laser It can be configured to separate the amplified light beam portion from the guide laser beam portion by transmitting substantially all of the beam diagnostic portion.

In another general form, extreme ultraviolet light produces a target material at a target location in a vacuum formed by the chamber; Supply pump energy to a gain medium of at least one optical amplifier in the drive laser system to produce an amplified light beam; Adjusting one or more characteristics of the amplified light beam; Directing the guide laser beam to a target position; Collect at least a portion of the guide laser beam reflected from one side of the converging lens and at least a portion of the amplified light beam; And by separating the collected amplified light beam portion from the collected guide laser beam portion. One or more characteristics are adjusted by directing the amplified light beam through a set of optical components, including directing the amplified light beam through a converging lens arranged and arranged to focus the amplified light beam at a target location. do. The collected amplified light beam portion comprises the collected amplified light beam portion and the collected guide laser beam portion such that one of the collected portions is transmitted through the dichroic optical device and the other collected portion is reflected from the dichroic optical device. It can be separated from the collected guide laser beam portion by directing it to the dichroic optical device.

Implementations may include one or more of the following features. For example, the separated portions can be sent to an optical sensor that outputs image data of the separated portions. The analysis module may be configured to perform one or more of determining the beam size of the image data for each separated portion, and determining the center of the image data for each separated portion. The position of one or more components of the optical component set may be adjusted based on one or more of the determined beam size and the determined center.

The amplified light beam may be oriented through a set of optical components by reflecting the amplified light beam to the mirror before the amplified light beam through the converging lens. Such portions can be collected by collecting portions that are reflected back from the converging lens and through the opening in the mirror.

1 is a block diagram of a laser generated plasma extreme ultraviolet light source.
FIG. 2A is a block diagram of one exemplary driving laser system that may be used for the light source of FIG. 1.
FIG. 2B is a block diagram of one exemplary driving laser system that may be used for the light source of FIG. 1.
3 is a block diagram of one exemplary beam delivery system located between a target position of the light source of FIG. 1 and a drive laser system.
4 is a block diagram of one exemplary metrology system that may be used in the beam delivery system of FIG. 3.
5A is a perspective view of one exemplary mirror used in the focus assembly of the beam delivery system of FIG. 3.
FIG. 5B is a top view of the mirror of FIG. 5A.
5C is a bottom plan view of the mirror of FIG. 5A.
5D is a side cross-sectional view taken along line 5D-5D in FIG. 5C.
6 is a diagram of a dichroic optical device that may be used in the metrology system of FIG. 3.
FIG. 7 is a wavelength versus reflectivity graph of S and P polarizations arriving at the dichroic optical device of FIG. 6.
8 is a block diagram of one exemplary focus assembly including the metrology system of FIG. 4.
9 is a block diagram of one exemplary focus assembly including the metrology system of FIG. 4.
10 is a block diagram of one exemplary focus assembly that includes the metrology system of FIG. 4.
11 is a flowchart of a procedure performed by a focus assembly.

Referring to FIG. 1, the LPP EUV light source 100 is a target location in the vacuum chamber 130 with an amplified light beam 110 to convert the target material into a plasma state containing an element having an emission line within the EUV range. It is formed by irradiating the target material 114 in 105. The light source 100 includes a drive laser system 115 that produces an amplified light beam due to population inversion in the gain medium (s) of the drive laser system 115.

The light source 100 also includes a beam delivery system between the laser system 115 and the target location 105, which includes the beam transport system 120 and the focus assembly 122. The beam transport system 120 receives the amplified light beam 110 from the laser system 115, steers and modifies the amplified light beam 110 as needed, and focuses the amplified light beam 110. Output to assembly 122. The focus assembly 122 receives the amplified light beam 110 and focuses the beam 110 to a target location 105.

As described below, the beam transport system 120 includes a beam expanding system that magnifies the beam 110, among other components, in particular, between the laser system 115 and the focus assembly 122. In addition, as described below, the focus assembly 122 includes a metrology system 124 that performs diagnostics on the lens 110 and the lens 110 that focuses the beam 110 onto the target location 105, among other components. ). Prior to providing details for beam transport system 120, focus assembly 122, and metrology system 124, a general description of light source 100 is provided with reference to FIG. 1.

Light source 100 delivers target material 114, for example, in the form of liquid droplets, liquid streams, solid particles or clusters, solid particles contained in liquid droplets, or solid particles contained within liquid streams. ). Target material 114 may include any material having emission lines within the EUV range, for example when converted to water, tin, lithium, xenon, or plasma states. For example, elemental tin is pure tin (Sn), tin compounds such as SnBr ₄ , SnBr ₂ , SnH ₄ , tin alloys such as tin-gallium alloys, tin-indium alloys, tin-indium-gallium alloys, Or any combination of these alloys. Target material 114 may include a wire coated with one of the above elements, such as tin. If the target material is in a solid state, it can have any suitable shape, such as a ring, sphere, or cube. The target material 114 may be conveyed into the vacuum chamber 130 and to the target location 105 by the target material conveying system 125. The target location 105 is also referred to as the location where the target material 114 is irradiated by the amplified light beam 110 to generate a plasma, ie the irradiation location.

In some implementations, the laser system 115 may include one or more main pulses, and in some cases one or more optical amplifiers, lasers, and / or lamps to provide one or more pre-pulses. Each optical amplifier includes a gain medium, an excitation source, and an internal optical member capable of optically amplifying a desired wavelength with high gain. The optical amplifier may or may not include a laser mirror or other feedback device forming a laser cavity. Therefore, the laser system 115 produces an amplified light beam 110 due to the distribution inversion in the gain medium of the laser even when no laser cavity is present. In addition, the laser system 115 may calculate an amplified light beam 110 that is a coherent laser beam if a laser cavity is present to provide sufficient feedback to the laser system 115. The term “amplified light beam” is not necessarily coherent laser oscillation but is only one of light from amplified laser system 115 and light from laser system 115 that is amplified and coherent laser oscillation. It includes the above.

The optical amplifier in the laser system 115 may include a filling gas comprising CO ₂ as a gain medium and may amplify light with a wavelength of about 9100 to about 11000 nm, in particular about 10600 nm, with a gain of 1000 or more. . Amplifiers and lasers suitable for use in the laser system 115 produce pulsed laser devices, such as radiation of approximately 9300 nm or approximately 10600 nm, and operate at relatively high power, eg, over 10 kW, for example, via DC or RF excitation. And, for example, a pulsed gas discharge C02 laser device with a high pulse repetition rate of 50 kHz or higher. The optical amplifier in the laser system 115 may also include a cooling system, such as water, that may be used when operating the laser system 115 at high power.

Referring to FIG. 2A, as one particular implementation, the laser system 115 has a master oscillator / power amplifier (MOPA) with multiple amplification steps, for example having a high repetition rate and low energy, capable of 100 kHz operation. It has a seed pulse initiated by a Q-switched master oscillator (MO) 200. From the MO 200, the laser pulses are, for example, RF pumped, high speed axial flow, CO ₂ amplifiers 202, 204 to produce an amplified light beam 210 traveling along the beam path 212. , 206).

Although three optical amplifiers 202, 204, and 206 are shown, fewer amplifiers and three or more amplifiers may be used in this implementation. In some implementations, each CO ₂ amplifier 202, 204, 206 can be an RF pumped axial flow CO ₂ laser cube with a 10 meter amplifier length folded by an internal mirror.

As an alternative, referring to FIG. 2B, the drive laser system 115 may be configured as a so-called “self-targeting” laser system in which the target material 114 serves as one mirror of the light cavity. In some "self-targeting" arrangements, a master oscillator may not be needed. The laser system 115 includes a chain of amplifier chambers 250, 252, 254 arranged in a line along the beam path 262, each chamber having its own gain medium and excitation source, such as a pumping electrode. Each amplifier chamber 250, 252, 254 is, for example, an RF pumped, high speed axial flow, CO with a combined one pass gain of, for example, 1,000-10,000 for amplifying light of wavelength λ of 10600 nm. _It may be _two amplifier chambers. Each amplifier chamber 250, 252, 254, when set up alone, can be designed without a laser cavity (resonator) such that the amplified light beam does not contain the optical components needed to pass through the gain medium more than once. . Nevertheless, as mentioned above, the laser cavity can be formed as follows.

In such an implementation, the laser cavity may be formed by adding the rear partially reflective optics 264 to the laser system 115 and placing the target material 114 at the target location 105. The optical member 264 is a planar mirror, curved mirror, phase-conjugated with approximately 95% reflectivity for a wavelength of approximately 10600 nm (wavelength of the light beam 110 amplified when a CO ₂ amplifier chamber is used). conjugate) or a corner reflector.

The target material 114 and the rear partially reflective optics 264 serve to reflect a portion of the amplified light beam 110 back from the laser cavity to the laser system 115. Therefore, the presence of the target material 114 at the target location 105 provides sufficient feedback for the laser system 115 to produce coherent laser oscillation, in which case the amplified light beam 110 has a laser Can be considered as a beam. When the target material 114 is not present at the target location 105, the laser system 115 may still be pumped to yield an amplified light beam 110, although some other components in the light source 100 may be sufficient. If you don't provide feedback, you won't make coherent laser oscillations. In particular, during the intersection of the amplified light beam 110 and the target material 114, the target material 114 may reflect light along the beam path 262 and pass through the amplifier chambers 250, 252, 254. Cooperate with the optical member 264 to form an optical cavity. This arrangement is such that the reflectance of the target material 114 is sufficient such that the optical gain does not exceed the light loss in the cavity, so that when the gain medium in each of the amplifier chambers 250, 252, 254 is excited, the target material ( While irradiating 114, a laser beam is generated, a plasma is generated, and an EUV light emission line in the chamber 130 is calculated. Through this arrangement, the optical member 264, the amplifiers 250, 252, 254, and the target material 114 allow the target material 114 to act as a mirror of the optical cavity (so-called plasma mirror or mechanical q-switch). To form a so-called "self-targeting" laser system that serves. Self-targeting laser systems are disclosed in US application Ser. No. 11 / 580,414, filed October 13, 2006 entitled "Drive Laser Delivery System for EUV Light Sources."

Depending on the application, other types of amplifiers or lasers, such as excimer or molecular fluorine lasers operating at high power and high pulse repetition rate, may be suitable. Examples include, for example, solid state lasers having gain media in the form of fibers or discs, such as US Pat. No. 6,625,191; 6,549,551; 6,549,551; And an excimer laser system in a MOPA configuration as shown in US Pat. No. 6,567,450, an excimer laser having one or more chambers, such as one oscillator chamber and one or more amplification chambers (amplification chambers may be in parallel or in series), master oscillator Power oscillator (MOPO) arrangement, power oscillator / power amplifier (POPA) arrangement; Alternatively, solid state lasers that seed one or more excimer or molecular fluorine amplifier or oscillator chambers may be suitable. Other designs are possible.

At the irradiation position, the amplified light beam 110 properly focused by the focus assembly 122 is used to produce a plasma having a certain characteristic that depends on the configuration of the target material 114. Such characteristics may include the wavelength of EUV light generated by the plasma and the amount of debris away from the plasma.

The light source 100 includes a collection mirror 135 having an aperture 140 for allowing the amplified light beam 110 to pass through to reach the target location 105. The collection mirror 135 may be, for example, an elliptical mirror having a first focal point at the target position 105 and a second focal point (also called intermediate focal point) at the intermediate position 145, wherein the EUV light may be light source 100. Can be output from, for example, input into an integrated circuit lithography tool (not shown). The light source 100 also reduces the amount of plasma generated debris entering the focus assembly 122 and / or beam delivery system 120 while allowing the amplified light beam 110 to reach the target location 105. To this end, it may include an open-ended hollow conical shroud 150 that tapers away from the collection mirror 135 toward the target location 105. For this purpose, a gas flow can be provided in the shroud directed towards the target location 105.

The light source 100 may also include a master controller 155 coupled to the drop position detection feedback system 156, the laser control system 157, and the beam control system 158. The master controller 155 may be a general purpose computer including software and memory, which includes instructions to cause one or more output devices coupled to the controller 155 to perform certain functions.

The light source 100 provides an output indicative of the position of the droplet, for example relative to the target position 105, and outputs this output, for example, the droplet position at which the droplet position error can be calculated on a drop-by-drop basis, or on average. And one or more target or droplet imagers 160 that provide the droplet position detection feedback system 156 to calculate the trajectory. Therefore, the drop position detection feedback system 156 provides drop position error as input to the master controller 155. Therefore, the master controller 155 may transmit the laser position, direction, and timing correction signals to, for example, the beam focus spot in the chamber 130 and / or to the laser control system 157 that may be used to control the laser timing circuit. The beam control system 158 to control the amplified light beam position and shape of the beam delivery system 120 to change its focus power and / or position.

The target material conveying system 125 may, for example, modify the release point of the droplets emitted by the conveying mechanism 127 to correct the error of the droplets reaching the desired target position 105. And a target material conveyance control system 126 operable in response to a signal from the apparatus.

In addition, the light source 100 may include a light source detector 165 that measures one or more EUV light parameters, which parameters may include pulse energy, energy distribution as a function of wavelength, energy within a particular wavelength band, outside a particular wavelength band. Angular distributions of energy, and EUV intensity and / or average power. The light source detector 165 generates a feedback signal for use by the master controller 155. Such feedback signals may indicate errors in parameters such as timing and focus of the laser pulses, for example to properly intercept the drops at the correct position and time for effective and efficient EUV light generation.

The light source 100 also includes a guide laser 175 that can be used to align the various sections of the light source 100 or to help steer the amplified light beam 110 to the target location 105. The guide laser 175 is distinct from the operating wavelength of the laser system 115 and has a guide wavelength that is within the wavelength range of the optical component within the laser system 115, the beam delivery system 120, and the focus assembly 122. Calculate the laser beam. In addition, the guide laser beam of the guide laser 175 must have sufficient power to pass through the optical components that need to be aligned, but is of relatively lower power than the amplified light beam 110. If the laser 175 is operated with greater power if the guide wavelength is far from the operating wavelength of the laser system 115 and is outside the wavelength range of the optical component, it is possible to operate with greater power, but the guide wavelength is driven outside the wavelength range of the optical component. It is not desirable to operate the guide laser 175 in this manner because the amount of power required increases nonlinearly (eg, exponentially) with the efficiency degradation that occurs. Guide laser 175 may operate while laser system 115 does not produce an amplified light beam 110.

Guide laser 175 can be used to align components within laser system 115, for example, to align the optical amplifier of the laser system 115 with other optical amplifiers. In this implementation, the guide laser 175 may be used to align the components during the initial setup of the light source 100 and prior to EUV calculation in the vacuum chamber 130. EUV calculation in chamber 130 is calculated by the amplified light beam 110 to convert the target material into a plasma emitting within the EUV range, as well as by the amplified light beam 110 to the target position 105. And needs to reach the target material 114. In addition, in this implementation, guide laser 175 may also be used to align components within the beam delivery system to steer the amplified light beam 110 through the beam delivery system to the target location 105. Therefore, in this implementation, the guide laser 175 is inverted while the gain medium of the laser system 115 is inverted (in the absence of the laser cavity), but does not yield coherent laser oscillation, or (the laser cavity is Present, and where the laser system is calculating coherent laser oscillation), may be used to align the components and the amplified light beam 110 during EUV calculation in chamber 130. The alignment may appear in the inverted gain medium and occurs while the gain medium is inverted to compensate for lensing that would not appear in the inverted gain medium.

The guide laser 175 can be used in a second implementation to align the optical components in the beam delivery system and to steer the amplified light beam 110 to the target location 105. In this implementation, the guide laser 175 is such that while the gain medium of the laser system 115 is not inverted and does not yield coherent laser oscillation, or there is a laser cavity and the laser system is coherent laser oscillation In the case of calculation, it can be used to align the amplified light beam 110 with other components during EUV calculation in chamber 130.

In connection with the guide laser 175, the light source 100 includes a metrology system 124 placed in the focus assembly 122 to sample a portion of the light from the guide laser 175 and the amplified light beam 110. do. In another implementation, metrology system 124 is placed within beam transport system 120.

The aforementioned criteria for the laser system 115, comprising as a gain medium in the optical amplifier a CO ₂ and comprising a fill gas capable of amplifying light of approximately 9100 to approximately 11500 nm, in particular approximately 11150 nm. A guide laser 175 can be selected that meets this requirement. Such CO ₂ lasers are commercially available from Sinrad Inc. of Mercalthio, Washington.

In a first implementation, the guide laser 175 is a widely tunable mid-IR outer cavity laser based on quantum cascade technology. The laser may be tuned to the wavelength of approximately 8100 nm, in the wavelength range that can be used in a set-up for sufficiently close to the operating wavelength of the amplifier CO _2, CO ₂ and amplifier optical component. These quantum cascade lasers are available from Daylight Solutions, Poway, California.

In a second implementation, the guide laser 175 is a tunable CO ₂ laser that can be grating tuned or gratingies tuned, wherein the guide laser 175 is a CO ₂ optical amplifier used in the laser system 115. The selectable wavelength range that can be distinguished selects special optical elements and / or CO ₂ isotope gas filling in the cavity. Such lasers can be purchased from Access Laser Company, Marysville, Washington. For example, if the guide laser 175 is a CO ₂ laser using CO ₂ isotopes as a gain medium, the guide wavelength may be selected to be approximately 11150 nm, or any wavelength between 9000 and 11500 nm.

The metrology system 124 may include a subset or portion of the amplified light beam 110 and an optical element that samples or redirects the guide laser beam, which includes the guide laser beam and the amplified light beam 110. It is made of any material that can withstand the power of). Since the wavelengths of the amplified light beam 110 and the guide laser beam are different from each other, they separate the diagnostic portion of the amplified light beam 110 from the diagnostic portion of the guide laser 175 and provide for individual analysis, It can be separated using a dichroic optical device placed in the focus assembly 122 (such as a dichroic mirror or dichroic filter). Because the beam analysis system analyzes the sampled light from the guide laser 175 and uses that information to adjust the components in the focus assembly 122 through the beam control system 158, It is formed of the metrology system 124 and the master controller 155.

Thus, in summary, the light source 100 yields an amplified light beam 110 directed to the target material at target location 105 to convert the target material into a plasma emitting light in the EUV range. The amplified light beam 110 operates at a particular wavelength determined based on the design and characteristics of the laser system 115, as described in more detail below. Further, the amplified light beam 110 is suitable when the target material provides sufficient feedback to the laser system 115 to produce coherent laser light, or when the driving laser system 115 forms a laser cavity. If it includes light feedback, it can be a laser beam.

As described above, the drive laser system 115 includes at least one amplifier and several optical components (eg, approximately 20 to 50 mirrors), wherein the beam delivery system 120 and the focus assembly 122 are For example, several optical components such as mirrors, lenses, and prisms. These optical components all include a wavelength range that includes the wavelength of the amplified light beam 110 to allow efficient formation of the amplified light beam 110 and output of the amplified light beam 110 to the target location 105. Has In addition, one or more optical components may be formed with a multilayer dielectric antireflective interference coating on the substrate.

Referring to FIG. 3, one exemplary beam delivery system 300 is placed between the drive laser system 305 and the target location 310, the beam delivery system comprising a beam transport system 315 and a focus assembly 320. ). The beam transport system 315 receives the amplified light beam 325 calculated by the driving laser system 305, redirects and enlarges the amplified light beam 325, and then enlarges and redirects the amplified light beam 325. Amplified light beam 325 is sent to focus assembly 320. The focus assembly 320 collects the amplified light beam 325 to the target location 310.

Beam transport system 315 includes optical components, such as mirrors 330 and 332 that redirect the amplified light beam 325, and other beam steering optics 334. The mirrors 330 and 332 and the beam steering optical member 334 may be made of any substrate and coating suitable for reflecting the amplified light beam 325. Therefore, they can be made of a substrate and a coating selected to reflect most of the light at the wavelength of the amplified light beam 325. In some implementations, the one or more mirrors 330, 332, and the beam directing optics 334 are formed of a maximum metal reflection produced by Saxonburg, Pennsylvania II-VI infrared on an oxygen free high conductivity (OFHC) copper substrate. High reflectivity coating such as MMR) coating. Other coatings that may be used include gold and silver, and other substrates to which the coating may be applied include silicon, molybdenum, and aluminum. The one or more mirrors 330, 332, and the beam steering optics 334 may be water cooled with water or some other suitable coolant flowing through the substrate.

The beam transport system 315 also has a lateral size of the amplified light beam 325 exiting the beam expanding system 340 than a lateral size of the amplified light beam 325 entering the beam expanding system 340. To be larger, it includes a beam expanding system 340 that enlarges the amplified light beam 325. Beam expanding system 340 may include a curved mirror having a reflective surface that is an off-axis segment of the elliptic paraboloid (this mirror is also referred to as an off-axis parabolic mirror). The beam magnification system 340 may include other optical components selected to reorient and magnify or collimate the amplified light beam 325. Various designs for the beam expanding system 340 are described in an application entitled "Beam Transport System for Extreme Ultraviolet Light Sources" filed simultaneously with this application.

As shown in FIG. 3, the focus assembly 320 is a converging lens constructed and arranged to focus the mirror 350 and the amplified light beam 325 reflected from the mirror 350 to the target location 310. 355 with a focusing element. The mirror 350, also called a pre-lens mirror, can be made of a substrate having a highly reflective coating at the wavelength of the amplified light beam 325. For example, the mirror 350 may have a maximum metal reflective (MMR) coating made by Saxonburg, Pennsylvania II-VI Infrared on an oxygen free high conductivity (OFHC) copper substrate. Other coatings that can be used for the mirror 350 include gold and silver, and other substrates to which the coating can be applied include silicon, molybdenum, and aluminum. The lens 355 is made of a metal that can transmit at the wavelength of the amplified light beam 325.

Focus assembly 320 may also include metrology system 360 to capture light 365 reflected from lens 355. Light 365 includes at least a diagnostic portion of amplified light beam 325 and a diagnostic portion of light from guide laser 175. This captured light is used to determine the location of the amplified light beam 325, for example, to characterize the light from the amplified light beam 325 and the guide laser 175. Can be used to monitor the change in focal length. Specifically, the captured light provides information about the position of the amplified light beam 325 on the lens 355 and the convergence lens 355 of the lens 355 due to a change in temperature (eg, heating) of the lens 355. Can be used to monitor focal length changes.

The light 365 reflected from the lens 355 converges to a focal point coinciding with the opening of the mirror 350 as described in more detail below. In this way, the opening of the mirror 350 provides a path for the light 365 to reach the metrology system 360, and also prevents or reduces self lasing within the beam delivery system 300. Prevent 365 from entering the beam transport system 315 again.

The metrology system 360 collects the light 365, separates the amplified light beam diagnostic portion from the guide laser beam portion, and directs the separated diagnostic portion 366 to the optical sensor 364. ). The light collection system 362 of the metrology system 360 separates the light 365 into a diagnostic amplified light beam and a diagnostic guide laser beam (dichroic mirror or dichroism) to allow individual analysis of each of these beams. Optical components such as dichroic optical devices. This dichroic optical device is configured to separate the diagnostic portion by transmitting substantially all of one diagnostic portion based on the wavelength of each of the diagnostic portions and reflecting substantially all of the other diagnostic portion. In the implementation shown below, the dichroic optical device reflects light at the wavelength of the amplified light beam 325 (eg, approximately 10600 nm), and the wavelength of light generated by the guide laser 175 (eg, approximately 11150 nm). Transmits light in

The light sensor 364 captures an image of the separated diagnostic portion 366 within the light collection system 362, and outputs an image signal directed towards the analysis module 395. Analysis module 395 includes software that performs real-time analysis on the image captured by light sensor 364 to determine magnitude and center coordinates. The analysis module 395 may be a standalone device coupled to the master controller 155, or may be integrated within the master controller 155. In some implementations, analysis module 395 is a National Instruments PXI Box.

The analysis module 395 and / or the controller 155 may include at least one component of the beam delivery system 300 (eg, the lens 355 and / or the one or more movable mirrors 350 based on the values of the magnitude and the center coordinates). Beam delivery system 300 in order to increase the EUV yield by changing the position or angle of the)), thereby increasing the overlap of the amplified light beam 325 with the target material 114 at the target location 105. Connected to at least one actuator 385, 390 connected to a component within (eg, mirror 350 and / or lens 355). Metrology system 360 includes other optical components, such as filters, lenses, beam splitters, and mirrors, to adjust the light in other ways before reaching the detector 364.

In general, the converging lens 355 may be an aspherical lens to reduce spherical aberration and other optical aberrations that may occur with the spherical lens. The converging lens 355 may be installed as a window on one wall of the chamber, or may be installed inside the chamber or outside the chamber. Lens 355 may be movable, whereby the lens may be installed on one or more actuators to provide a mechanism for active focus control during operation of the system. In this way, the lens 355 can be moved to more effectively gather the amplified light beam 325 and direct the light beam 325 to the target location to increase or maximize EUV yield. The magnitude and direction of the displacement of the lens 355 is determined based on the feedback provided by the metrology system 360, as described below.

The converging lens 355 has a diameter that is large enough to capture the majority of the amplified light beam 325 but provides a curvature sufficient to focus the amplified light beam 325 to a target position. In some implementations, the converging lens 355 can have a numerical aperture of at least 0.25. In some implementations, the converging lens 355 is made of ZnSe, a material that can be used for infrared applications. ZnSe has a transmission range covering 0.6 to 20 μm and can be used for high power light beams calculated from high power amplifiers. ZnSe has a low heat absorption in the red end of the electromagnetic spectrum (especially infrared). Other materials that can be used for the converging lens include, but are not limited to, gallium arsenide and diamond. In addition, the converging lens 355 may include an antireflective coating and may transmit at least 95% of the amplified light beam 325 at the wavelength of the amplified light beam 325.

Therefore, at least one of the mirrors 330, 332, 350, and components within the beam steering optics 334 may provide a master controller to provide active pointing control of the amplified light beam 325 to the target location 310. It may be movable through the use of a movable mount actuated by an actuation system with a motor that can be controlled by 155. The movable mirror and beam steering optics can be adjusted to maintain the focus of the amplified light beam 325 on the target material and the position of the amplified light beam 325 on the lens 355.

Beam delivery system 300 may also be used in beam delivery system 300 (such as mirrors 330 and 332, beam steering optics 334, components within beam magnification system 340, and front lens mirror 350). It can include an alignment laser 370 that is used at setup to align the position angle or position of one or more components. Alignment laser 370 may be a diode laser that operates within the visible light spectrum to help visually align components.

The beam delivery system 300 may also include a detection device 375, such as a camera, that monitors the light reflected from the target material 114 at the target location 310, which light is detected at the detection device 375. Reflected at the front of the drive laser system 305 to form a diagnostic beam 380 that may be. The detection device 375 may be connected to the master controller 155.

 The design of metrology system 360, mirror 350, and lens 355 does not require the use of additional optics in the path of the amplified light beam 325 to capture light 365 for diagnostic purposes. It provides a more compact design than conventional diagnostic arrangements. In addition, all diagnostic portions 366 may be captured through one optical sensor 364 to reduce the number of components needed for analysis. As mentioned above, the dichroic optical device is configured to separate the diagnostic portions by transmitting substantially all of one diagnostic portion based on the wavelength of each diagnostic portion and substantially reflecting all the other diagnostic portions. Therefore, it is possible to separate the diagnostic light without the use of a diffraction grating, whereby the stability of the diagnostic portion is improved and the distortion in the diagnostic portion is reduced through the use of a dichroic optical device.

 In addition, the characteristics of the lens 355 are such that enough light 365 for the metrology system 360 is reflected back from the lens 355 while the amplified light beam 325 transmits as much as possible to the target location 310. It is specified by the manufacturer of the lens 355 to ensure that it is.

Referring to FIG. 4, one exemplary metrology system 460 is reflected from lens 355 and onto aperture 348 of mirror 350 to pass through aperture 348 and enter metrology system 460. Receive focused 365 for diagnostic purposes.

Referring also to FIGS. 5A-D, the mirror 350 includes a first plano face 500 and a metrology system 460 where the amplified light beam 325 collides and is reflected towards the lens 355. And face a second face 505 opposite the first face 500. The mirror 350 includes a through hole 548 that intersects the first face 500 and the second face 505, the through hole 548 having a first cross section at a larger cross-sectional area at the second face 505. It has a generally conical shape that is tapered with a smaller cross-sectional area at face 500.

The mirror 350 may be made of anoxic high conductivity (OFHC) copper and the first face 500 may be finished with a maximum metal reflector (MMR) such as manufactured by II-VI infrared of Saxon, Pennsylvania. Can be. The mirror 350 has a clear aperture 515 large enough to reflect the entire amplified light beam 325 towards the lens 355.

Referring again to FIG. 4, the metrology system 460 includes a collimating or converging lens 405 and a flat optical member or window 410. The collimating lens 405 may be a plano convex lens made of ZnSe. The flat optical member 410 is formed of two flat surfaces that are completely transmissive to the light 365. The flat optical member 410 may additionally include a relatively small central blocking region 412 that blocks light 414 reflected from the target material at the target location, as described below.

Referring also to FIG. 6, the metrology system 460 transmits substantially all of one diagnostic portion 600 based on the wavelength of each diagnostic portion, and reflects substantially all of the other diagnostic portion 605, thereby providing light. Dichroic optical device 415 (such as a dichroic mirror or dichroic filter) configured to separate diagnostic portions of 365. In the implementation described below, the dichroic optical device 415 transmits substantially all (ie, greater than approximately 99%) of the guide laser beam and reflects substantially all (ie, greater than approximately 99%) of the amplified light beam. do. However, it should be understood that the dichroic optical device 415 may be configured to transmit substantially (ie greater than 99%) the entire amplified light beam and reflect substantially (ie greater than 99%) the entire guide laser beam. do.

As shown in the exemplary graph 700 of FIG. 7, in some implementations, if the amplified light beam 325 has a wavelength of approximately 10600 nm, the dichroic optical device 415 is indicated by an arrow 705. And reflects more than 99% of the light (including p and s polarization components) at a wavelength of 10600 nm. In addition, if the guide laser beam has a wavelength of approximately 11150 nm, the dichroic optical device 415 may have more than 99% of the light (including p and s polarization components) of wavelength 11150 nm (indicated by arrow 710). It is configured to transmit light.

 Metrology system 460 may also include filters 420, 425, 430 located downstream of the dichroic optical device 415 to provide additional filtering of the diagnostic portion. The filters 420, 425 may be additional dichroic optical devices placed in the path of the transmitted guide laser beam portion 600, for example to reflect the amplified light beam portion transmitted through the optical device 415. have. Such filters 420 and 425 may be used to adjust the relative power of the transmitted and reflected portions to obtain a useful signal in the optical sensor 364. This adjustment is useful when the amplified light beam 325 is considerably stronger than the guide laser beam. In this case, since the amplified light beam 325 is considerably stronger than the guide laser beam, it is possible for enough amplified light beam 325 to transmit through the dichroic optical device 415, which is part 600. This makes it more difficult to accurately measure the characteristics of the guide laser beam. Filter 430 may be an additional dichroic optical device that lies within the path of reflected amplified light beam portion 605, for example, to block unwanted light from portion 605. In addition, the filter 430 may have an antireflective coating on its back side to block light of other unwanted wavelengths (eg, approximately 10200 nm) in which the laser system 115 operates. In addition, the filters 420, 425, 430 can be angled relative to the beam path such that reflection is directed out of the beam path. Similar to the dichroic optical device 415, the filters 420, 425, 430 can be made of ZnSe.

The metrology system 460 also follows each path of the diagnostic portion 600, 605 to divide the diagnostic portions 600, 605 of each beam into two beams, both of which are directed to the optical sensor 364. It may include partial reflectors 435, 440. In this way, the four beams 470, 475, 480, 485 are four unknowns, the center of the diagnostic amplified light beam, the center of the diagnostic guide laser beam, the size of the diagnostic amplified light beam, the size of the diagnostic guide laser beam. These four beams are sent to an optical sensor 364 that can use these to calculate the size. Four beams 470, 475, 480, 485 hit the light sensitive surface of the light sensor to allow individual analysis to be performed for each beam to determine the size and center of each beam. When directed, the beams are directed such that they are spatially separated from one another (eg, four beams are separated from each other by dark areas).

The partial reflector 440 may be configured to reflect approximately 70% and transmit approximately 30% of the amplified light beam portion 605. The partial reflector 435 may be configured to reflect approximately 30% and transmit approximately 70% of the guide laser beam portion 600. Each partial reflector 435, 440 may be made of ZnSe or any other suitable material for the wavelength involved. Depending on the number of unknown values that must be determined by analysis module 395 and / or controller 155, additional or fewer splitting devices may be used.

In addition, although partial reflectors 435, 440 are used to split each beam, other partial reflectors 445, 450, 455, 465 can be inserted in the path to provide additional filtering, if necessary. have. The metrology system 460 may include other components such as lenses for modifying the shape of the wavefront of the light and mirrors for modifying and / or redirecting the shape of the wavefront of the light. The lens may be made of ZnSe and the mirror may be made of silicon (Si), but other materials are possible.

The light sensor 364 may be any detector with sufficient resolution to analyze the characteristics of the image formed from the diagnostic portion. For example, the optical sensor 364 may have a resolution of at least 100,000 nm. In some implementations, the optical sensor 364 is a pyroelectric array camera having a spectral range that includes the wavelength of the diagnostic portion. For example, the pyroelectric array camera can be a Pyrocam ™ III series camera from Opta-Spiricon Incorporated in Utah. Pyroelectric array cameras can include laser beam analysis software that can be used for other characteristics and analysis capabilities. Alternatively, the output from the pyroelectric array camera can be sent to analysis module 395 or master controller 155 for analysis of the captured image.

8, the metrology system 460 is configured and arranged to focus the mirror 350 and the amplified light beam 325 reflected from the mirror 350 to a target location 810 in the chamber 830. Is shown with one exemplary focus assembly 820 that includes a converging lens 855. In this example, the converging lens 855 is a double sided convex lens. Lens 855 is placed on wall 890 of chamber 830 such that lens 855 serves as a window between the vacuum maintained inside chamber 830 and the purified environment outside of chamber 830. Three directions with respect to the direction of the light beam 325; The vacuum chamber wall 890 to facilitate movement of the lens 855 along one or more of two directions, axial or longitudinal and transverse to the axial direction, extending along the direction of the light beam 325. A bellow may be placed between the lenses 855.

Metrology system 460 captures light 865 reflected from lens 855, transmitted through an opening in the center of mirror 350, as described above.

The extreme ultraviolet light vacuum chamber 830 collects the extreme ultraviolet light emitted from the target material at the target location 810 when the amplified light beam 325 strikes the target material across the target location 810. The constructed extreme ultraviolet light collector 835 is housed.

 Referring also to FIG. 9, in another implementation, metrology system 960 is designed similar to metrology system 460 to capture light 965 reflected from lens 955 of exemplary focus assembly 920. It is. In this implementation, the focus assembly 920 includes a lens front mirror 950 configured to reflect the reflected light 965 instead of transmitting the reflected light (as performed by the mirror 350). The mirror 950 may be designed to have a central portion designed to reflect the amplified light beam 325 towards the lens 955 and to reflect light 965 towards the metrology system 960. The focus assembly 920 also includes an additional movable mirror 980 placed between the lens 955 and the target position 910 to redirect light from the lens 955 toward the target position 910.

Lens 955 may be a plano-convex aspherical lens having a numerical aperture of at least 0.25. In this implementation, the lens 955 is placed in the extreme ultraviolet light vacuum chamber 930, but may be placed on the wall of the chamber 930 to provide an air-tight seal. The extreme ultraviolet light vacuum chamber 930 is configured to collect the extreme ultraviolet light emitted from the target material at the target location 910 when the amplified light beam 325 strikes the target material across the target location 910. Housed is an extreme ultraviolet light collector 935.

 Referring to FIG. 10, as another implementation, the focus assembly 1020 may include the amplified light beam 325 reflected from the mirror 1050 and the mirror 1050 and from another intermediate mirror 1085 in the target chamber 1030. And a focus element comprising a converging lens 1055 configured and arranged to focus to position 1010. In the present implementation, the converging lens 1055 is mounted on the wall 1090 of the chamber 1030 such that the lens 1055 serves as a window between the vacuum maintained in the chamber 1030 and the purified environment outside the chamber 103. It is a flat iron lens. Three directions with respect to the direction of the light beam 325; Vacuum chamber wall 1090 and lens 1055 to facilitate movement of lens 1055 along one or more of two directions transverse to the axial direction and axial direction extending along the direction of light beam 325. Bellows (not shown) can be placed between them. Focus assembly 1020 includes a metrology system 1060 that reflects from lens 1055 and captures light 1065 directed through a central opening in mirror 1050. Metrology system 1060 generally operates the same way as other metrology systems in that the metrology system includes a dichroic optical device 1015 that separates the diagnostic amplified light beam from the diagnostic guide laser beam of reflected light 1065. It works.

The extreme ultraviolet light vacuum chamber 1030 collects the extreme ultraviolet light emitted from the target material at the target location 1010 when the amplified light beam 325 strikes the target material across the target location 1010. The configured extreme ultraviolet light collector 1035 is housed.

Referring again to FIG. 3, in its use, the light 365 reflected from the lens 355 is directed through an optical component in the metrology system, where the light is spaced four spatially into the optical sensor 364. Divided into beams separated by.

For example, referring again to FIG. 4, the light 365 reflected from the lens 355 is focused into a focus area in the opening 348 of the mirror 350, and the light 365 points the collimating lens 405. Passes through opening 348 as directed broadened beam. The collimation lens 405 provides sufficient divergence for the light 365 such that the light 365 exiting the lens 405 is substantially parallel. The collimating lens 405 also reflects light reflected from the target material such that the light 414 exiting the lens 405 converges to the focus area blocked by the central blocking area 412 of the flat optical member 410. 414 provides sufficient divergence.

As another example, in FIGS. 9 and 10, the light 965, 1065 reflected from the lenses 955, 1055 takes a different path but in all cases the light eventually ends up in each metrology system 460, 960, 1060. Dichroic optical devices 415, 915, 1015 are reached.

After proceeding through the optical component in the metrology system, the four diagnostic beams arrive at the optical sensor 364, which is a Faticam III camera from Oppi-Spiricon Incorporated in one implementation described above. The image acquired by the light sensor 364 is converted into a data format suitable for analysis by a processor (eg, analysis module 395 and / or master controller 155), and in some implementations, 14 usable bits It can be in I16 format (signed 16-bit integer). Image data output by light sensor 364 is sent to analysis module 395.

Referring to FIG. 11, analysis module 395 (or master controller 155 if analysis software is implemented in controller 155) performs procedure 1100 for calculating the size and center of each captured image. The image is defined by having a distinct dark border around it. Initially, analysis module 395 receives a set of respective image data from optical sensor 364 (step 1105). Each image data set then represents one of the diagnostic beams that impinge upon the optical sensor 364.

The analysis module 395 then performs a data transformation on the image data to make it a format suitable for other analysis (step 1110). Data conversion involves converting data in an image into data in one array's format. Data conversion also converts bit swaps to positive pixel values, that is, from one data format (such as the I16 format) to another (such as the U16 format, an unsigned 16-bit integer format). Do what you do. Data transformation also includes summing elements within the array to obtain a one-dimensional array. For example, array elements in the Y image direction are summed to obtain a one-dimensional Y array, and array elements in the X image direction are summed to obtain a one-dimensional X array. In addition, the data transformation may include a baseline correction calculation that uses the average value of the longevity of one subset of pixels (eg, the first 3-10 pixels) to ensure zero baseline. In addition, data conversion may include normalization of the array to a maximum or average value.

After data transformation (step 1110), analysis module 395 constructs a function that fits closely to the data points or elements of the array, such as by interpolating the data of the array.

The analysis module 395 then calculates the beam size of the interpolated image data for each diagnostic beam along each of the X and Y directions (step 1120). The beam size can be calculated at a certain level, such as 5%, 10%, 1 / e ² , 20%, or 50%. The given scale for the fatigue cam III is 0.1 mm / pixel and the value of the beam size can be reported to the controller 155 in millimeters.

The analysis module 395 also calculates the center (weight center) of the interpolated image data for each diagnostic beam (step 1125). The center is calculated based on the intensity of each pixel and the coordinates of each pixel. The given scale for the fatigue cam III is 0.1 mm / pixel and the center value can be reported to the controller 155 in millimeters.

In addition, analysis module 395 may calculate the overall intensity of the image for each diagnostic beam (step 1130) and may calculate the area of the image for each diagnostic beam (step 1135). The overall intensity of the image can be calculated by integrating under the data obtained after performing array summation and zeroing the baseline, or by integrating under the interpolated curve obtained after step 1115. The area of the image may be calculated based on the beam size within the X and Y positions calculated at step 1120 at a particular level (eg, 1 / e ² ).

Output from analysis module 395 (eg, beam size and center) may be sent to a master controller 155 that uses the output to tune one or more components of the beam delivery system. For example, tuning of the mirror 350 is performed based on 10600 nm diagnostic information (from the amplified light beam), and tuning of the lens 355 is 11150 nm diagnostic (from the guide laser beam) without using 10600 nm information. It is performed based on the information. The mirror 350 and / or lens 355 are tuned (adjusted) to optimize or increase the overlap of the amplified light beam 325 with the target material 310.

Other implementations are within the scope of the following claims.

Although a detector 165 is shown in FIG. 1 that is positioned to receive light directly from the target location 105, alternatively the detector 165 is at the intermediate focal point 145, or downstream of the intermediate focal point, or some other. It may be positioned to sample light at the location.

In general, irradiation of the target material 114 may also generate debris at the target location 105, which may contaminate the surface of the optical element including the collection mirror 135 by way of non-limiting example. . Therefore, a gaseous etchant source capable of reacting with the constituents of the target material 114 may cause the chamber 130 to clean contaminants deposited on the surface of the optical element, as described in US Pat. No. 7,491,954. Can be introduced within. For example, in one application, the target material may include Sn and the etchant may be HBr, Br ₂ , Cl ₂ , HC1, H ₂ , HCF ₃ , or some combination of such compounds.

Light source 100 may also include one or more heaters 170 that initiate and / or increase the rate of chemical reaction between the deposited target material and the etchant on the surface of the optical element. For plasma target material comprising Li, the heater 170 may be designed to heat the surface of the one or more optical members to a temperature in the range of approximately 400 to 500 ° C. to evaporate Li from the surface. At this time, it is not necessary to use an etchant. Suitable types of heaters may include radiator-type heaters, microwave heaters, RF heaters, resistive heaters, or combinations of such heaters. The heater may be directed to a particular optical element face, and therefore may be directional, or non-directional, and may heat the entire chamber 130 or a substantial portion of the chamber 130.

Claims (31)

As an extreme ultraviolet light system,
A drive laser system for producing an amplified light beam;
A target material conveying system configured to produce a target material at a target location in a vacuum space formed in the chamber;
A beam delivery system comprising a set of optical components and configured to receive the amplified light beam emitted from the drive laser system and to direct the amplified light beam toward the target position;
As a measurement system,
And collect at least a diagnostic portion of the amplified light beam that does not reach the target position, and at least a diagnostic portion of a guide laser beam that does not reach the target position, and transmits substantially all of one of the diagnostic portions. A light collection system having a dichroic optical device configured to separate said diagnostic portion by substantially reflecting another of said diagnostic portions, and
A metrology system comprising an optical sensor for capturing at least two diagnostic portions separated by the dichroic optical device; And
A controller coupled to the optical sensor and to the at least one component for changing the position of the at least one component in the beam delivery system based on the output of the optical sensor,
The vacuum chamber houses an extreme ultraviolet light collector configured to collect extreme ultraviolet light emitted from the target material when the amplified light beam strikes the target material across the target location,
And said at least two diagnostic portions have distinct wavelengths. The system of claim 1 wherein the beam delivery system is
A beam expanding system for expanding the size of the amplified light beam; And
And a focusing element configured and arranged to focus the amplified light beam to the target position. 3. The extreme ultraviolet light system of claim 2, wherein the focusing element comprises a converging aspheric lens. 4. The extreme ultraviolet light system according to claim 3, wherein the converging lens is made of zinc selenide. 4. The extreme ultraviolet light system according to claim 3, wherein the converging lens forms a pressure resistant window of the vacuum chamber for separating the vacuum inside the vacuum chamber from an environment outside the vacuum chamber. 4. The system of claim 3, wherein the beam delivery system includes an actuation system mechanically coupled to the converging lens, the actuation system receiving a control signal from the controller and based on the control signal, the amplified light beam. And to move the converging lens to adjust the focus of the extreme ultraviolet light system. 4. The extreme ultraviolet light system of claim 3, wherein the light collection system is configured to collect the amplified light beam reflected by one surface of the converging lens. 4. The extreme ultraviolet light system of claim 3, wherein the beam delivery system includes a lens front mirror that redirects the amplified light beam from the beam expanding system back toward the converging lens. 10. The system of claim 8, wherein the beam delivery system comprises an actuation system mechanically coupled to the front mirror of the lens, wherein the actuation system receives a control signal from the controller and based on the control signal, the amplified light. And to move the mirror in front of the lens to adjust the focus of the beam. The method of claim 1, wherein the controller is configured to change the position of the at least one component to increase the generation of extreme ultraviolet light in the chamber by increasing overlap between the amplified light beam and the target material at the target location. And provide an output signal to an actuation system coupled to the at least one component. The method of claim 1, further comprising a guide laser for calculating the guide laser beam,
The amplified light beam is a first distinct wavelength and the guide laser beam is a second distinct wavelength; And
The dichroic optical device reflects substantially all of the diagnostic portion of the amplified light beam and transmits substantially all of the diagnostic portion of the guide laser beam to thereby diagnose the portion of the amplified light beam from the diagnostic portion of the guide laser beam. Extreme ultraviolet light system, characterized in that configured to separate. As a method of calculating the extreme ultraviolet light,
Calculating a target material at a target location in the vacuum formed by the chamber;
Supplying pump energy to a gain medium of at least one optical amplifier in the drive laser system to produce an amplified light beam;
Adjusting one or more characteristics of the amplified light beam and directing the amplified light beam through the set of optical components to the target location;
Directing a guide laser beam to the target location;
Collecting at least a portion of the amplified light beam that does not reach the target position, and at least a portion of the guide laser beam that does not reach the target position; And
One of the collected portions transmits through a dichroic optical device and the other of the collected portions reflects through the dichroic optical device such that the collected amplified light beam portion and the collected guide laser beam are Separating the collected amplified light beam portion from the collected guide laser beam portion by directing the dichroic optical device to the dichroic optical device. 13. The method of claim 12, further comprising directing the separated portions to an optical sensor that outputs image data of the separated portions. 14. The method of claim 13, further comprising sending the image data of each of the separated portions to an analysis module, wherein the analysis module further comprises:
Determining the beam size of the image data for each of the separated portions; And
And configured to perform one or more of determining the center of the image data for each of the separated portions. 15. The method of claim 14, further comprising adjusting the position of one or more components of the optical component based on at least one of the determined beam size and the determined center. . 13. The method of claim 12, wherein directing the amplified light beam through the set of optical components to the target location
Reflecting the amplified light beam from a mirror; And
Directing the reflected amplified light beam through a focusing element for capturing the amplified light beam and focusing the amplified light beam to the target location. . 17. The method of claim 16, wherein collecting the portion comprises collecting the portion reflected from the converging lens and reflected back through an opening in the mirror. As an extreme ultraviolet light system,
A drive laser system for producing an amplified light beam;
A target material conveying system configured to produce a target material at a target location in a vacuum space formed in the chamber;
Receive the amplified light beam emitted from the drive laser system, and direct the amplified light beam toward the target position, and configured and arranged to focus the amplified light beam at the target position. A beam delivery system comprising a set of optical components with a converging lens; And
A metrology system having a light collection system configured to collect a portion of the amplified light beam reflected from the converging lens and a portion of the guide laser beam reflected from the converging lens;
The vacuum chamber houses an extreme ultraviolet light collector configured to collect extreme ultraviolet light emitted from the target material when the amplified light beam strikes the target material across the target location,
And said light collection system comprises a dichroic optical device configured to separate said portions by transmitting a first portion and reflecting a second portion. The method of claim 18,
An optical sensor for capturing the portions separated by the dichroic optical device; And a controller coupled to the optical sensor and to at least one component in the beam delivery system for repositioning the at least one component based on an output from the optical sensor. Ultraviolet light system. 20. The apparatus of claim 19, wherein the controller is
The at least one of the beam delivery system for changing the position of the at least one component to increase the generation of extreme ultraviolet light in the chamber by increasing overlap between the amplified light beam and the target material at the target location. And an output signal to an actuation system connected to a component of the extreme ultraviolet light system. 19. The apparatus of claim 18, further comprising an actuation system mechanically coupled to the converging lens, the actuation system receiving a control signal from a controller and adjusting the focus of the amplified light beam based on the control signal. An extreme ultraviolet light system, configured to move the converging lens. 19. The amplified beam of claim 18, wherein the beam delivery system comprises a lens front mirror that redirects the amplified light beam from the beam expanding system back toward the converging lens, and the amplified beam reflected from the converging lens. A portion and the guide laser beam portion are oriented through an opening in the front mirror of the lens before reaching the dichroic optical device. 23. The system of claim 22, wherein the beam delivery system includes an actuation system mechanically coupled to the front mirror of the lens, the actuation system receiving a control signal from the controller and based on the control signal And to move the mirror in front of the lens to adjust the focus of the beam. The method of claim 18,
The beam delivery system comprises a beam expanding system for enlarging the size of the amplified light beam; And
The converging lens is configured and arranged to receive the enlarged amplified light beam from the beam expanding system. 19. The method of claim 18, further comprising a guide laser for calculating the guide laser beam,
The amplified light beam is a first distinct wavelength, the guide laser beam is a second distinct wavelength, and
The dichroic optical device reflects substantially all of the diagnostic portion of the amplified light beam and transmits substantially all of the diagnostic portion of the guide laser beam, thereby separating the amplified light beam portion from the guide laser beam portion. Extreme ultraviolet light system, characterized in that configured to. As a method of calculating the extreme ultraviolet light,
Calculating a target material at a target location in the vacuum formed by the chamber;
Supplying pump energy to a gain medium of at least one optical amplifier in the flex laser system to produce an amplified light beam;
By directing the amplified light beam through a set of optical components, comprising directing the amplified light beam through a converging lens configured and arranged to focus the amplified light beam at the target position. Adjusting one or more characteristics of the amplified light beam;
Directing a guide laser beam to the target location;
Collecting at least a portion of the amplified light beam and at least a portion of the guide laser beam, reflecting from one surface of the converging lens; And
One of the collected portions transmits through a dichroic optical device and the other of the collected portions reflects through the dichroic optical device such that the collected amplified light beam portion and the collected guide laser beam are Separating the collected amplified light beam portion from the collected guide laser beam portion by directing the to a dichroic optical device. 27. The method of claim 26, further comprising directing the separated portions to an optical sensor that outputs image data of the separated portions. 28. The method of claim 27, further comprising sending the image data of each of the separated portions to an analysis module, wherein the analysis module further comprises:
Determining the beam size of the image data for each of the separated portions, and
And configured to perform one or more of determining the center of the image data for each of the separated portions. 29. The method of claim 28, further comprising adjusting the position of one or more components of the optical component based on at least one of the determined beam size and the determined center. . 27. The method of claim 26, wherein directing the amplified light beam through a set of optical components reflects the amplified light beam from a mirror prior to directing the amplified light beam through the converging lens. And extreme ultraviolet light, characterized in that it comprises a step. 31. The method of claim 30, wherein collecting the portion comprises collecting a portion reflected back from the converging lens through an opening in the mirror.

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